Switching circuit



July 9, 1940.

G. G. GOODLING, JR El- AL SWITCHING CIRCUIT Filed May 28, 1937 w ll filBH W! kh .QQI Lw mm mam v $5 m uwe oh h ww M a mi N. V X 0. kmfikouhk aa M m a PM M H w L M N J v M 9 wk s ufi m\ r (Titorneg Patented July'9,1940 SWITCHING CIRCUIT George G. Goodling, Jr.', Woodlynne, and ArthurC. Stocker, Haddon Heights, N. J., assignors to Radio Corporation ofAmerica, a corporation of Delaware Application May 28, 1937, Serial No.145,394

6 Claims.

Our invention relates to switching devices, and particularly to meansfor actuating a plurality of switches in sequence.

The most common way of actuating several switches in a desired sequenceis to employ a motor driven cam which closes or opens the switches insuccession mechanically. For many applications this is undesirablebecause of the resulting noise, vibration, etc.

It is, accordingly, an object of our invention v to provide an improvedmethod of and means for actuating a plurality of switches or the like insuccession.

It is a iurther object of our invention to provide improved apparatusfree from rotating parts for actuating a plurality of switchessuccessively.

It is a still further object of our invention to provide improved meansfor connecting a plurality of circuits successively to another circuit.

In the preferred embodiment of our invention, a plurality of vacuumtubes are employed, each tube having in its plate circuit a relaywinding and associated switch arms. In the input circuit of each tubethere is a condenser so connected through one of the switches in thepreceding plate circuit that it' may charge up to block the tube, thisaction taking place when the relay in the said preceding plate circuitis deenergized. If this relay is energized, the condenser is dischargedwhereby the said tube is unblocked as soon as the relay next becomesdeenergized.

The vacuum tubes are connected in what may be referred to asback-to-back relation, the plate circuit of each tube being connected tothe input circuit of another tube. Thus, once" the switching operationis initiated, it continues without interruption. I

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawing in which the singlefigureis a circuit diagram of a preferred embodiment of the invention.

Referring to the drawing, it will first be explained just what switchingoperations are desired. For the purpose of illustration, it is assumedthat three crystal controlled oscillators (not shown), which areidentified as oscillators #1, #2 and #3, are to be connectedsuccessively to a recorder indicated at Thus the crystals of the threeoscillators may be placed in an oven and their temperature-frequencycharacteristics recorded on a single recorder.

.Oscillator #1 is connected to a switch arm l which may be connected tothe recorder I V ounded contact point through a contact point H and aconductor l2. Oscillator #2 is connected to a switch arm i3 which may beconnected to the recorder through a contact point I4 and the conductorl2. Oscillator #3 is connected to a switch arm |6 which may be similarlyconnected to the recorder I through a contact point I! and the conductor|2.

Reference will now be made to the circuit for operating switches l0, l3and I6 in sequence. It

includes three electric discharge tubes |8, I9 and 2|] which may be ofthe high vacuum type. These tubes have indirectly heated cathodes 2|, 22and 23 which are connected t9 ground.

Considering first the connections for the tube |9, this tube has acontrol grid 24 and a plate 26. The grid 24 is connected through a gridleak resistor 21 to a point on a voltage divider 28 which is negativewith respect to ground. The

grid 24 is also connected to a contact point 29 associated with a switcharm 3|. A condenser 32 is connected between the switch arm 3| andground.

When the switch arm 3| is in the lower position, it connects condenser32 between the grid 24and ground whereby the potential applied to grid24 is the voltage across condenser 32. Also, when switch arm 3| is inthis position, the condenser 32 is being charged from the voltage sourceacross voltage divider 28. Eventually, condenser 32 will apply such anegative potential to grid 24 that the tube l9 will be blocked.

When'the switch arm 3| is in the upper position, it short-circuitscondenser 32 through a I 33, thus discharging the condenser.

The switch arms in and 3| are pulled to their upper positionssimultaneously by a relay wind-v ing 34 when. it is energized. Whenrelay winding 34 is deenergized, the switch arms In and 3| drop to theirlower positions.

v relay winding 36, as shown. Similarly, plate voltage is applied to theplates 38 and 39 of tubes |8 and 2|), respectively, through the relaywinding 34 and a relaywinding 4|, respectively.

The control grid 42 of tube 20 is connected through a grid leak resistor43 to a point. on the 'voltage divider 44. Grid 42 is also connected toa contact point 46 with which the switch 3'! makes contact in its lowerposition.

Between the switch arm 31 and ground there is connected a condenser 57which is charged through the grid resistor 43 to block the tube 212.When switch arm 31 is pulled to the upper position, it strikes-agrounded contact point 48 and the condenser 47 is discharged. The relaywinding 38 and its associated switch arms l3-and 34 function the same asthe previously described relay 35, H3, in.

A starting key 39 is connected to the input circuit of one of the vacuumtubes, tube in the circuit illustrated, for unblocklng a tube toinitiate the circuit operation as will lee described hereinafter.

The control grid 5! of tube it is connected through a grid leak resistor52 to a point on a voltage divider 53. The grid id is also connectedthrough a conductor 5 to a contact'point 56 associatedwith a switch arm5']. A condenser 53 is connected between the switch arm 57 and ground.

The switch arm 5? makes contact with the grounded contact point '59 inits upper position.

The switch arms it and 5'! are pulled upward simultaneously by the relaycoil dl when it is energized.

From the foregoing description it will be seen that the switch in eachinput circuit which controls the charge of the input circuit condenseris actuated by the current flow in the preceding tube. Thus, thecondition of one tube determines the operating condition of the nextfollowing tube.

The operation of the circuit will be better understood by followingthrough one complete cycle of operation. When the circuit is in itsnormal inactive state, as illustrated in the drawing, each vacuum tubeis blocked, that is, the condensers l2, l1 and 58 are fully chargedv andapply suiliciently negative potentials to the control grids for biasingthe tubes substantially to plate current cut-off. Therefore, all therelay switch arms are in their lower position.

To start the switching operation, the starting key 49 is closedmomentarily, thus connecting the control grid .42 to ground and at thesame time discharging the condenser 41. As a result, the tube 20 isunblocked and the relay coil ll pulls up the switch arms l6 and 51 toconnect oscillator #3 to the recorder l and to discharge condenser 5:.These switch arms are held in their upper position until tube 20 isagain blocked, this blocking action taking place aiter a certain period,since condenser 41 is being charged through the grid leak resistor 43.from the voltage source 44. The time required for charging condenser, toa voltage which blocks the tube 2! is determined by the time constant ofthe charging circuit for this condenser. Because of this, it is a simplematter to control the length of time that oscillator #3 is connected tothe recorder.

As soon as tube 20 blocks, the switch arms I and 51 drop to their lowerposition whereby the control grid of tube I I is connected substantial-1y to ground through the conductor 54 and the discharged condenser 58..This unblocks the tube II and the relay coil 34, pulls up the switcharms II and 3|, thereby connecting oscillator #1 to the recorder anddischarging condenser 32. Thwe switch arms are held in their upperposition until tube It is again blocked, the time required for thisdepending upon the time constant of the circuit through which condenser50 is being charged,

As soon as the tube 18 again blocks, the switch arms I. and II fall totheir lower position, thereby connecting the discharged condenser 32 tothe control grid oi tube I9 to unblock this tube and energize the relaycoil 36. The switch arms l3 and..31 are then pulled to their upperposition ,sition whereby the control grid of tube 20 is'conr'iected toground through the discharged eondenser M to unblock the tube 20. Thecycle or" operation is now repeated audit continues until the action isstopped by breaking a circuit, removing voltage from a tube, or thelike.

It may be noted that any suitable voltage sources such as batteries orsocket power units may be employed for supplying the'plate and biasingVoltages. If socket power units are employed, voltage should not beapplied to the plates of the tubes until the voltage supplied by theseunits has reached a stable value because abnormally'high voltages willstart the circuit in operation before the starting key is closed.

It will be apparent that our invention may be employed for switching anynumber of circuits in sequence by employing any number of tubes.

so long as at least two tubes are employed.

We claim as our invention: I 1. In combination, a plurality of vacuumtubes each having at least three electrodes including a controlelectrode, a plurality of relays, each relay comprlsing a relay coil anda switch, each of said tubes having-an input circuit including a controlelectrode and a plate circuit, said tubes being connected in cascaderelation through said relays, each relay having its coil in the platecircuit of one tube and its switch in the input potential to its controlelectrode and for causing it normallyto be blocked, and means forcausing said tubes to unblock in succession in response to theunblocklng of a certain one of said tubes,

said tubes in cascade being connected in a closed control electrode, andeach tube having a plate circuit including a relay winding, each tubehaving means including a switch in its input circuit for blocking thetube in response tothe'switch being moved to one position, said tubesbeing connected in cascade relation with the relay winding of one tubepositioned to actuate the switch in the input circuit of asucceedingtube. the relay winding of the last tube being positioned toactuate the switch of the first tube, and means including saidrelaywindings and switches for unblocking a tube in response to theblocking of a preceding tube, said tubes in cascade being connected in aclosed circuit or back-'to-back relation with a relay having its coil inthe plate circuit of the last tube and having its switch in the inputcircuit of the first tube.

3. Switching apparatus comprising a plurality of electric dischargetubes each having an input circuit and an output circuit and each havinga cathode and a grid, a relay winding donnected in each of said platecircuits, each of said input circultsincluding a condenser and means forcharg--' circuit of a succeeding tube, and means in'the input circuit ofeach tube for applying a negative,

is applied between the cathode and the grid of the associated tube thesaid associated tube is blocked, switching means in each of said inputcircuits for discharging the condenser therein in response toenergization of the relay winding in the next preceding plate circuit,and means in each of said input circuits for connecting the condensertherein between the cathode and the grid of the associated tube and inseries with said charging means in response to the energization of therelay winding in the next preceding plate circuit.

4. A plurality of vacuum tubes each having a cathode,-a control grid anda plate circuit each of said tubes having a source of voltage and a.grid resistor connected between the cathode and the grid with thepolarity of said source such as to make the grid negative, each of saidtubes having a condenser and a switch connected in series between thecathode and the grid whereby the voltage across the condenser is appliedto the grid when the switch is closed, a relay winding in each of saidplate circuits, each relay winding being so associated with the switchin the next succeeding input circuit that said switch is closed inresponse to the deenergization of the associated relay winding, andmeans for discharging each of said condensers in response to theenergization of the relay winding in the next preceding plate circuit.

5. A switching circuit comprising a plurality of vacuum tubes eachhaving a plate circuit and a grid circuit, each of said grid circuitsincluding a cathode and a grid, a relay winding in each of said platecircuits, a switch in each of said grid circuits, the relay winding inthe plate circuit of each tube being positioned to actuate the switch inthe grid circuit of a difierent-tube, means in each of said gridcircuits including a condenser for blocking the tube in response to theswitch in the grid circuit of that tube resting in one position for apredetermined time, the condenser in each of said grid circuits havingone terminal connected to the cathode of its grid circuit and having theother terminal connected to the grid of the grid circuit through theswitch in its grid circuit, and means for discharging the condenser inthe grid circuit of that tube in response to said switch moving to adifferent position.

6. Switching apparatus comprising a plurality of vacuum tubes eachhaving an input and an output circuit, a relay winding in each outputcircuit, contacts operated thereby to perform useful switching ofexternal circuits, and other contacts operated thereby to performswitching in the input circuit of the succeeding tube, said inputcircuit comprising a grid connected through a resistor to a source ofbias voltage sufiicient to succeeding tube, and connected block saidthrough said input circuit switching contacts to a condenser, said inputcircuit switching being so arranged that upon energization of the relaycoil said condenser is disconnected from said succeeding grid andconnected to a potential nearer that of the cathode of said succeedingtube, said con; denser being thereby somewhat discharged Withoutaltering the operating condition of said succeeding tube, and further,said input switching being so arranged that, upon deenergization of uthe relay coil, said condenser is disconnected from said potential andreconnected to the grid of said succeeding tube, said grid being therebytransferred to said potential permitting unblocking of said succeedingtube and consequent energization of the relay winding in its outputcircuit, said unblocking remaining in eifect during the time required torecharge said condenser through said grid resistor. I

GEORGE G. GOODLING, JR.

ARTHUR C. STOCKER.

